/*
 * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.micode.notes.data;

import android.content.ContentValues; // 用于存储一组键值对，通常用于插入或更新数据库记录
import android.content.Context; // 提供对应用程序环境的全局信息访问
import android.database.sqlite.SQLiteDatabase; // 用于管理 SQLite 数据库的类
import android.database.sqlite.SQLiteOpenHelper; // 用于创建和管理 SQLite 数据库版本的辅助类
import android.util.Log; // 用于记录日志信息

import net.micode.notes.data.Notes.DataColumns; // 导入数据列相关的接口
import net.micode.notes.data.Notes.DataConstants; // 导入数据常量相关的类
import net.micode.notes.data.Notes.NoteColumns; // 导入笔记列相关的接口

// 定义一个继承自 SQLiteOpenHelper 的类，用于管理笔记数据库
public class NotesDatabaseHelper extends SQLiteOpenHelper {
    // 数据库名称
    private static final String DB_NAME = "note.db";
    // 数据库版本号
    private static final int DB_VERSION = 4;

    // 定义一个接口，用于存储数据库表名
    public interface TABLE {
        // 笔记表名
        public static final String NOTE = "note";
        // 数据表名
        public static final String DATA = "data";
    }

    // 用于日志记录的标签
    private static final String TAG = "NotesDatabaseHelper";

    // 单例实例
    private static NotesDatabaseHelper mInstance;

    // 创建笔记表的 SQL 语句
    private static final String CREATE_NOTE_TABLE_SQL =
        "CREATE TABLE " + TABLE.NOTE + "(" +
            NoteColumns.ID + " INTEGER PRIMARY KEY," + // 唯一标识列，整数类型，主键
            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 父 ID 列，整数类型，默认值为 0
            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," + // 提醒日期列，整数类型，默认值为 0
            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," + // 背景颜色 ID 列，整数类型，默认值为 0
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期列，整数类型，默认值为当前时间戳（毫秒）
            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," + // 是否有附件列，整数类型，默认值为 0
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期列，整数类型，默认值为当前时间戳（毫秒）
            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," + // 文件夹中的笔记数量列，整数类型，默认值为 0
            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," + // 文件夹名称或笔记文本内容列，文本类型，默认值为空字符串
            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," + // 文件类型列，整数类型，默认值为 0
            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," + // 小部件 ID 列，整数类型，默认值为 0
            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," + // 小部件类型列，整数类型，默认值为 -1
            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," + // 同步 ID 列，整数类型，默认值为 0
            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," + // 本地修改标志列，整数类型，默认值为 0
            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 移动到临时文件夹之前的原始父 ID 列，整数类型，默认值为 0
            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," + // gtask ID 列，文本类型，默认值为空字符串
            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" + // 版本号列，整数类型，默认值为 0
        ")";

    // 创建数据表的 SQL 语句
    private static final String CREATE_DATA_TABLE_SQL =
        "CREATE TABLE " + TABLE.DATA + "(" +
            DataColumns.ID + " INTEGER PRIMARY KEY," + // 唯一标识列，整数类型，主键
            DataColumns.MIME_TYPE + " TEXT NOT NULL," + // MIME 类型列，文本类型，不能为空
            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," + // 所属笔记 ID 列，整数类型，默认值为 0
            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期列，整数类型，默认值为当前时间戳（毫秒）
            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期列，整数类型，默认值为当前时间戳（毫秒）
            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," + // 数据内容列，文本类型，默认值为空字符串
            DataColumns.DATA1 + " INTEGER," + // 通用数据列 1，整数类型
            DataColumns.DATA2 + " INTEGER," + // 通用数据列 2，整数类型
            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," + // 通用数据列 3，文本类型，默认值为空字符串
            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," + // 通用数据列 4，文本类型，默认值为空字符串
            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" + // 通用数据列 5，文本类型，默认值为空字符串
        ")";

    // 创建数据表里 note_id 索引的 SQL 语句
    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";

    // 当将笔记移动到文件夹时，增加文件夹的笔记数量的触发器 SQL 语句
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER increase_folder_count_on_update "+
        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
        " END";

    // 当将笔记从文件夹移出时，减少文件夹的笔记数量的触发器 SQL 语句
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER decrease_folder_count_on_update " +
        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
        "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
        " END";

    // 当插入新笔记到文件夹时，增加文件夹的笔记数量的触发器 SQL 语句
    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
        "CREATE TRIGGER increase_folder_count_on_insert " +
        " AFTER INSERT ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
        " END";

    // 当从文件夹删除笔记时，减少文件夹的笔记数量的触发器 SQL 语句
    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER decrease_folder_count_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN " +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
        "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
        " END";

    // 当插入类型为 {@link DataConstants#NOTE} 的数据时，更新笔记内容的触发器 SQL 语句
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
        "CREATE TRIGGER update_note_content_on_insert " +
        " AFTER INSERT ON " + TABLE.DATA +
        " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
        " END";

    // 当类型为 {@link DataConstants#NOTE} 的数据发生变化时，更新笔记内容的触发器 SQL 语句
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_update " +
        " AFTER UPDATE ON " + TABLE.DATA +
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
        " END";

    // 当类型为 {@link DataConstants#NOTE} 的数据被删除时，更新笔记内容的触发器 SQL 语句
    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
        "CREATE TRIGGER update_note_content_on_delete " +
        " AFTER delete ON " + TABLE.DATA +
        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.SNIPPET + "=''" +
        "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
        " END";

    // 当删除笔记时，删除该笔记所属数据的触发器 SQL 语句
    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
        "CREATE TRIGGER delete_data_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN" +
        "  DELETE FROM " + TABLE.DATA +
        "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
        " END";

    // 当删除文件夹时，删除该文件夹下所有笔记的触发器 SQL 语句
    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
        "CREATE TRIGGER folder_delete_notes_on_delete " +
        " AFTER DELETE ON " + TABLE.NOTE +
        " BEGIN" +
        "  DELETE FROM " + TABLE.NOTE +
        "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
        " END";

    // 当文件夹被移动到回收站时，移动该文件夹下所有笔记的触发器 SQL 语句
    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
        "CREATE TRIGGER folder_move_notes_on_trash " +
        " AFTER UPDATE ON " + TABLE.NOTE +
        " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
        " BEGIN" +
        "  UPDATE " + TABLE.NOTE +
        "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
        "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
        " END";

    // 构造函数，用于初始化数据库辅助类
    public NotesDatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    // 创建笔记表的方法
    public void createNoteTable(SQLiteDatabase db) {
        db.execSQL(CREATE_NOTE_TABLE_SQL); // 执行创建笔记表的 SQL 语句
        reCreateNoteTableTriggers(db); // 重新创建笔记表的触发器
        createSystemFolder(db); // 创建系统文件夹
        Log.d(TAG, "note table has been created"); // 记录日志，表明笔记表已创建
    }

    // 重新创建笔记表触发器的方法
    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
        // 删除旧的触发器
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
        db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");

        // 创建新的触发器
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER);
        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER);
        db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER);
        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
    }

    // 创建系统文件夹的方法
    private void createSystemFolder(SQLiteDatabase db) {
        ContentValues values = new ContentValues(); // 创建一个 ContentValues 对象，用于存储要插入的数据

        // 创建通话记录文件夹
        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建根文件夹
        values.clear(); // 清空 ContentValues 对象
        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建临时文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);

        // 创建回收站文件夹
        values.clear();
        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
        db.insert(TABLE.NOTE, null, values);
    }

    // 创建数据表的方法
    public void createDataTable(SQLiteDatabase db) {
        db.execSQL(CREATE_DATA_TABLE_SQL); // 执行创建数据表的 SQL 语句
        reCreateDataTableTriggers(db); // 重新创建数据表的触发器
        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL); // 执行创建数据表里 note_id 索引的 SQL 语句
        Log.d(TAG, "data table has been created"); // 记录日志，表明数据表已创建
    }

    // 重新创建数据表触发器的方法
    private void reCreateDataTableTriggers(SQLiteDatabase db) {
        // 删除旧的触发器
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");

        // 创建新的触发器
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
    }

    // 获取单例实例的方法
    static synchronized NotesDatabaseHelper get